11 files changed, 596 insertions, 0 deletions
diff --git a/doc/src/sgml/catalogs.sgml b/doc/src/sgml/catalogs.sgml
index 4e6fd0e06fb..898865eea19 100644
--- a/doc/src/sgml/catalogs.sgml
+++ b/doc/src/sgml/catalogs.sgml
@@ -274,6 +274,11 @@
      </row>
 
      <row>
+      <entry><link linkend="catalog-pg-transform"><structname>pg_transform</structname></link></entry>
+      <entry>transforms (data type to procedural language conversions)</entry>
+     </row>
+
+     <row>
       <entry><link linkend="catalog-pg-trigger"><structname>pg_trigger</structname></link></entry>
       <entry>triggers</entry>
      </row>
@@ -5072,6 +5077,15 @@
      </row>
 
      <row>
+      <entry><structfield>protrftypes</structfield></entry>
+      <entry><type>oid[]</type></entry>
+      <entry></entry>
+      <entry>
+       Data type OIDs for which to apply transforms.
+      </entry>
+     </row>
+
+     <row>
       <entry><structfield>prosrc</structfield></entry>
       <entry><type>text</type></entry>
       <entry></entry>
@@ -6071,6 +6085,74 @@
  </sect1>
 
 
+ <sect1 id="catalog-pg-transform">
+  <title><structname>pg_transform</structname></title>
+
+  <indexterm zone="catalog-pg-transform">
+   <primary>pg_transform</primary>
+  </indexterm>
+
+  <para>
+   The catalog <structname>pg_transform</structname> stores information about
+   transforms, which are a mechanism to adapt data types to procedural
+   languages.  See <xref linkend="sql-createtransform"> for more information.
+  </para>
+
+  <table>
+   <title><structname>pg_transform</> Columns</title>
+
+   <tgroup cols="4">
+    <thead>
+     <row>
+      <entry>Name</entry>
+      <entry>Type</entry>
+      <entry>References</entry>
+      <entry>Description</entry>
+     </row>
+    </thead>
+
+    <tbody>
+     <row>
+      <entry><structfield>trftype</structfield></entry>
+      <entry><type>oid</type></entry>
+      <entry><literal><link linkend="catalog-pg-type"><structname>pg_type</structname></link>.oid</literal></entry>
+      <entry>OID of the data type this transform is for</entry>
+     </row>
+
+     <row>
+      <entry><structfield>trflang</structfield></entry>
+      <entry><type>oid</type></entry>
+      <entry><literal><link linkend="catalog-pg-language"><structname>pg_language</structname></link>.oid</literal></entry>
+      <entry>OID of the language this transform is for</entry>
+     </row>
+
+     <row>
+      <entry><structfield>trffromsql</structfield></entry>
+      <entry><type>regproc</type></entry>
+      <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
+      <entry>
+       The OID of the function to use when converting the data type for input
+       to the procedural language (e.g., function parameters).  Zero is stored
+       if this operation is not supported.
+      </entry>
+     </row>
+
+     <row>
+      <entry><structfield>trftosql</structfield></entry>
+      <entry><type>regproc</type></entry>
+      <entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
+      <entry>
+       The OID of the function to use when converting output from the
+       procedural language (e.g., return values) to the data type.  Zero is
+       stored if this operation is not supported.
+      </entry>
+     </row>
+    </tbody>
+   </tgroup>
+  </table>
+ </sect1>
+
+
  <sect1 id="catalog-pg-trigger">
   <title><structname>pg_trigger</structname></title>
 
diff --git a/doc/src/sgml/hstore.sgml b/doc/src/sgml/hstore.sgml
index fbe9543dfea..94f01f8dfe7 100644
--- a/doc/src/sgml/hstore.sgml
+++ b/doc/src/sgml/hstore.sgml
@@ -597,6 +597,25 @@ ALTER TABLE tablename ALTER hstorecol TYPE hstore USING hstorecol || '';
  </sect2>
 
  <sect2>
+  <title>Transforms</title>
+
+  <para>
+   Additional extensions are available that implement transforms for
+   the <type>hstore</type> type for the languages PL/Perl and PL/Python.  The
+   extensions for PL/Perl are called <literal>hstore_plperl</literal>
+   and <literal>hstore_plperlu</literal>, for trusted and untrusted PL/Perl.
+   If you install these transforms and specify them when creating a
+   function, <type>hstore</type> values are mapped to Perl hashes.  The
+   extensions for PL/Python are
+   called <literal>hstore_plpythonu</literal>, <literal>hstore_plpython2u</literal>,
+   and <literal>hstore_plpython3u</literal>
+   (see <xref linkend="plpython-python23"> for the PL/Python naming
+   convention).  If you use them, <type>hstore</type> values are mapped to
+   Python dictionaries.
+  </para>
+ </sect2>
+
+ <sect2>
   <title>Authors</title>
 
   <para>
diff --git a/doc/src/sgml/information_schema.sgml b/doc/src/sgml/information_schema.sgml
index 22f43c8a5bf..ca1f20b3385 100644
--- a/doc/src/sgml/information_schema.sgml
+++ b/doc/src/sgml/information_schema.sgml
@@ -5519,6 +5519,91 @@ ORDER BY c.ordinal_position;
   </table>
  </sect1>
 
+ <sect1 id="infoschema-transforms">
+  <title><literal>transforms</literal></title>
+
+  <para>
+   The view <literal>transforms</literal> contains information about the
+   transforms defined in the current database.  More precisely, it contains a
+   row for each function contained in a transform (the <quote>from SQL</quote>
+   or <quote>to SQL</quote> function).
+  </para>
+
+  <table>
+   <title><literal>transforms</literal> Columns</title>
+
+   <tgroup cols="3">
+    <thead>
+     <row>
+      <entry>Name</entry>
+      <entry>Data Type</entry>
+      <entry>Description</entry>
+     </row>
+    </thead>
+
+    <tbody>
+     <row>
+      <entry><literal>udt_catalog</literal></entry>
+      <entry><type>sql_identifier</type></entry>
+      <entry>Name of the database that contains the type the transform is for (always the current database)</entry>
+     </row>
+
+     <row>
+      <entry><literal>udt_schema</literal></entry>
+      <entry><type>sql_identifier</type></entry>
+      <entry>Name of the schema that contains the type the transform is for</entry>
+     </row>
+
+     <row>
+      <entry><literal>udt_name</literal></entry>
+      <entry><type>sql_identifier</type></entry>
+      <entry>Name of the type the transform is for</entry>
+     </row>
+
+     <row>
+      <entry><literal>specific_catalog</literal></entry>
+      <entry><literal>sql_identifier</literal></entry>
+      <entry>Name of the database containing the function (always the current database)</entry>
+     </row>
+
+     <row>
+      <entry><literal>specific_schema</literal></entry>
+      <entry><literal>sql_identifier</literal></entry>
+      <entry>Name of the schema containing the function</entry>
+     </row>
+
+     <row>
+      <entry><literal>specific_name</literal></entry>
+      <entry><literal>sql_identifier</literal></entry>
+      <entry>
+       The <quote>specific name</quote> of the function.  See <xref
+       linkend="infoschema-routines"> for more information.
+      </entry>
+     </row>
+
+     <row>
+      <entry><literal>group_name</literal></entry>
+      <entry><literal>sql_identifier</literal></entry>
+      <entry>
+       The SQL standard allows defining transforms in <quote>groups</quote>,
+       and selecting a group at run time.  PostgreSQL does not support this.
+       Instead, transforms are specific to a language.  As a compromise, this
+       field contains the language the transform is for.
+      </entry>
+     </row>
+
+     <row>
+      <entry><literal>transform_type</literal></entry>
+      <entry><type>character_data</type></entry>
+      <entry>
+       <literal>FROM SQL</literal> or <literal>TO SQL</literal>
+      </entry>
+     </row>
+    </tbody>
+   </tgroup>
+  </table>
+ </sect1>
+
  <sect1 id="infoschema-triggered-update-columns">
   <title><literal>triggered_update_columns</literal></title>
 
diff --git a/doc/src/sgml/ltree.sgml b/doc/src/sgml/ltree.sgml
index cd8a061c943..3f87319bf96 100644
--- a/doc/src/sgml/ltree.sgml
+++ b/doc/src/sgml/ltree.sgml
@@ -665,6 +665,21 @@ ltreetest=&gt; SELECT ins_label(path,2,'Space') FROM test WHERE path &lt;@ 'Top.
  </sect2>
 
  <sect2>
+  <title>Transforms</title>
+
+  <para>
+   Additional extensions are available that implement transforms for
+   the <type>ltree</type> type for PL/Python.  The extensions are
+   called <literal>ltree_plpythonu</literal>, <literal>ltree_plpython2u</literal>,
+   and <literal>ltree_plpython3u</literal>
+   (see <xref linkend="plpython-python23"> for the PL/Python naming
+   convention).  If you install these transforms and specify them when
+   creating a function, <type>ltree</type> values are mapped to Python lists.
+   (The reverse is currently not supported, however.)
+  </para>
+ </sect2>
+
+ <sect2>
   <title>Authors</title>
 
   <para>
diff --git a/doc/src/sgml/ref/allfiles.sgml b/doc/src/sgml/ref/allfiles.sgml
index f09fc250f08..bf95453b6c6 100644
--- a/doc/src/sgml/ref/allfiles.sgml
+++ b/doc/src/sgml/ref/allfiles.sgml
@@ -79,6 +79,7 @@ Complete list of usable sgml source files in this directory.
 <!ENTITY createTable        SYSTEM "create_table.sgml">
 <!ENTITY createTableAs      SYSTEM "create_table_as.sgml">
 <!ENTITY createTableSpace   SYSTEM "create_tablespace.sgml">
+<!ENTITY createTransform    SYSTEM "create_transform.sgml">
 <!ENTITY createTrigger      SYSTEM "create_trigger.sgml">
 <!ENTITY createTSConfig     SYSTEM "create_tsconfig.sgml">
 <!ENTITY createTSDictionary SYSTEM "create_tsdictionary.sgml">
@@ -120,6 +121,7 @@ Complete list of usable sgml source files in this directory.
 <!ENTITY dropServer         SYSTEM "drop_server.sgml">
 <!ENTITY dropTable          SYSTEM "drop_table.sgml">
 <!ENTITY dropTableSpace     SYSTEM "drop_tablespace.sgml">
+<!ENTITY dropTransform      SYSTEM "drop_transform.sgml">
 <!ENTITY dropTrigger        SYSTEM "drop_trigger.sgml">
 <!ENTITY dropTSConfig       SYSTEM "drop_tsconfig.sgml">
 <!ENTITY dropTSDictionary   SYSTEM "drop_tsdictionary.sgml">
diff --git a/doc/src/sgml/ref/alter_extension.sgml b/doc/src/sgml/ref/alter_extension.sgml
index 0d479c8ca2d..7141ee352eb 100644
--- a/doc/src/sgml/ref/alter_extension.sgml
+++ b/doc/src/sgml/ref/alter_extension.sgml
@@ -52,6 +52,7 @@ ALTER EXTENSION <replaceable class="PARAMETER">name</replaceable> DROP <replacea
   TEXT SEARCH DICTIONARY <replaceable class="PARAMETER">object_name</replaceable> |
   TEXT SEARCH PARSER <replaceable class="PARAMETER">object_name</replaceable> |
   TEXT SEARCH TEMPLATE <replaceable class="PARAMETER">object_name</replaceable> |
+  TRANSFORM FOR <replaceable>type_name</replaceable> LANGUAGE <replaceable>lang_name</replaceable> |
   TYPE <replaceable class="PARAMETER">object_name</replaceable> |
   VIEW <replaceable class="PARAMETER">object_name</replaceable>
 
@@ -259,6 +260,26 @@ ALTER EXTENSION <replaceable class="PARAMETER">name</replaceable> DROP <replacea
       </para>
      </listitem>
     </varlistentry>
+
+    <varlistentry>
+     <term><replaceable>type_name</replaceable></term>
+
+     <listitem>
+      <para>
+       The name of the data type of the transform.
+      </para>
+     </listitem>
+    </varlistentry>
+
+    <varlistentry>
+     <term><replaceable>lang_name</replaceable></term>
+
+     <listitem>
+      <para>
+       The name of the language of the transform.
+      </para>
+     </listitem>
+    </varlistentry>
    </variablelist>
   </para>
  </refsect1>
diff --git a/doc/src/sgml/ref/comment.sgml b/doc/src/sgml/ref/comment.sgml
index 62e1968c08d..656f5aae5ba 100644
--- a/doc/src/sgml/ref/comment.sgml
+++ b/doc/src/sgml/ref/comment.sgml
@@ -55,6 +55,7 @@ COMMENT ON
   TEXT SEARCH DICTIONARY <replaceable class="PARAMETER">object_name</replaceable> |
   TEXT SEARCH PARSER <replaceable class="PARAMETER">object_name</replaceable> |
   TEXT SEARCH TEMPLATE <replaceable class="PARAMETER">object_name</replaceable> |
+  TRANSFORM FOR <replaceable>type_name</replaceable> LANGUAGE <replaceable>lang_name</replaceable> |
   TRIGGER <replaceable class="PARAMETER">trigger_name</replaceable> ON <replaceable class="PARAMETER">table_name</replaceable> |
   TYPE <replaceable class="PARAMETER">object_name</replaceable> |
   VIEW <replaceable class="PARAMETER">object_name</replaceable>
@@ -225,6 +226,26 @@ COMMENT ON
      </listitem>
     </varlistentry>
 
+    <varlistentry>
+     <term><replaceable>type_name</replaceable></term>
+
+     <listitem>
+      <para>
+       The name of the data type of the transform.
+      </para>
+     </listitem>
+    </varlistentry>
+
+    <varlistentry>
+     <term><replaceable>lang_name</replaceable></term>
+
+     <listitem>
+      <para>
+       The name of the language of the transform.
+      </para>
+     </listitem>
+    </varlistentry>
+
    <varlistentry>
     <term><replaceable class="parameter">text</replaceable></term>
     <listitem>
@@ -305,6 +326,7 @@ COMMENT ON TEXT SEARCH CONFIGURATION my_config IS 'Special word filtering';
 COMMENT ON TEXT SEARCH DICTIONARY swedish IS 'Snowball stemmer for Swedish language';
 COMMENT ON TEXT SEARCH PARSER my_parser IS 'Splits text into words';
 COMMENT ON TEXT SEARCH TEMPLATE snowball IS 'Snowball stemmer';
+COMMENT ON TRANSFORM FOR hstore LANGUAGE plpythonu IS 'Transform between hstore and Python dict';
 COMMENT ON TRIGGER my_trigger ON my_table IS 'Used for RI';
 COMMENT ON TYPE complex IS 'Complex number data type';
 COMMENT ON VIEW my_view IS 'View of departmental costs';
diff --git a/doc/src/sgml/ref/create_function.sgml b/doc/src/sgml/ref/create_function.sgml
index 20019215351..c5beb166cfa 100644
--- a/doc/src/sgml/ref/create_function.sgml
+++ b/doc/src/sgml/ref/create_function.sgml
@@ -25,6 +25,7 @@ CREATE [ OR REPLACE ] FUNCTION
     [ RETURNS <replaceable class="parameter">rettype</replaceable>
       | RETURNS TABLE ( <replaceable class="parameter">column_name</replaceable> <replaceable class="parameter">column_type</replaceable> [, ...] ) ]
   { LANGUAGE <replaceable class="parameter">lang_name</replaceable>
+    | TRANSFORM { FOR TYPE <replaceable class="parameter">type_name</replaceable> } [, ... ]
     | WINDOW
     | IMMUTABLE | STABLE | VOLATILE | [ NOT ] LEAKPROOF
     | CALLED ON NULL INPUT | RETURNS NULL ON NULL INPUT | STRICT
@@ -261,6 +262,23 @@ CREATE [ OR REPLACE ] FUNCTION
     </varlistentry>
 
     <varlistentry>
+     <term><literal>TRANSFORM { FOR TYPE <replaceable class="parameter">type_name</replaceable> } [, ... ] }</literal></term>
+
+     <listitem>
+      <para>
+       Lists which transforms a call to the function should apply.  Transforms
+       convert between SQL types and language-specific data types;
+       see <xref linkend="sql-createtransform">.  Procedural language
+       implementations usually have hardcoded knowledge of the built-in types,
+       so those don't need to be listed here.  If a procedural language
+       implementation does not know how to handle a type and no transform is
+       supplied, it will fall back to a default behavior for converting data
+       types, but this depends on the implementation.
+      </para>
+     </listitem>
+    </varlistentry>
+
+    <varlistentry>
      <term><literal>WINDOW</literal></term>
 
      <listitem>
diff --git a/doc/src/sgml/ref/create_transform.sgml b/doc/src/sgml/ref/create_transform.sgml
new file mode 100644
index 00000000000..d321dad7a56
--- /dev/null
+++ b/doc/src/sgml/ref/create_transform.sgml
@@ -0,0 +1,207 @@
+<!-- doc/src/sgml/ref/create_transform.sgml -->
+
+<refentry id="SQL-CREATETRANSFORM">
+ <indexterm zone="sql-createtransform">
+  <primary>CREATE TRANSFORM</primary>
+ </indexterm>
+
+ <refmeta>
+  <refentrytitle>CREATE TRANSFORM</refentrytitle>
+  <manvolnum>7</manvolnum>
+  <refmiscinfo>SQL - Language Statements</refmiscinfo>
+ </refmeta>
+
+ <refnamediv>
+  <refname>CREATE TRANSFORM</refname>
+  <refpurpose>define a new transform</refpurpose>
+ </refnamediv>
+
+ <refsynopsisdiv>
+<synopsis>
+CREATE [ OR REPLACE ] TRANSFORM FOR <replaceable>type_name</replaceable> LANGUAGE <replaceable>lang_name</replaceable> (
+    FROM SQL WITH FUNCTION <replaceable>from_sql_function_name</replaceable> (<replaceable>argument_type</replaceable> [, ...]),
+    TO SQL WITH FUNCTION <replaceable>to_sql_function_name</replaceable> (<replaceable>argument_type</replaceable> [, ...])
+);
+</synopsis>
+ </refsynopsisdiv>
+
+ <refsect1 id="sql-createtransform-description">
+  <title>Description</title>
+
+  <para>
+   <command>CREATE TRANSFORM</command> defines a new transform.
+   <command>CREATE OR REPLACE TRANSFORM</command> will either create a new
+   transform, or replace an existing definition.
+  </para>
+
+  <para>
+   A transform specifies how to adapt a data type to a procedural language.
+   For example, when writing a function in PL/Python using
+   the <type>hstore</type> type, PL/Python has no prior knowledge how to
+   present <type>hstore</type> values in the Python environment.  Language
+   implementations usually default to using the text representation, but that
+   is inconvenient when, for example, an associative array or a list would be
+   more appropriate.
+  </para>
+
+  <para>
+   A transform specifies two functions:
+   <itemizedlist>
+    <listitem>
+     <para>
+      A <quote>from SQL</quote> function that converts the type from the SQL
+      environment to the language.  This function will be invoked on the
+      arguments of a function written in the language.
+     </para>
+    </listitem>
+
+    <listitem>
+     <para>
+      A <quote>to SQL</quote> function that converts the type from the
+      language to the SQL environment.  This function will be invoked on the
+      return value of a function written in the language.
+     </para>
+    </listitem>
+   </itemizedlist>
+   It is not necessary to provide both of these functions.  If one is not
+   specified, the language-specific default behavior will be used if
+   necessary.  (To prevent a transformation in a certain direction from
+   happening at all, you could also write a transform function that always
+   errors out.)
+  </para>
+
+  <para>
+   To be able to create a transform, you must own and
+   have <literal>USAGE</literal> privilege on the type, have
+   <literal>USAGE</literal> privilege on the language, and own and
+   have <literal>EXECUTE</literal> privilege on the from-SQL and to-SQL
+   functions, if specified.
+  </para>
+ </refsect1>
+
+ <refsect1>
+  <title>Parameters</title>
+
+   <variablelist>
+    <varlistentry>
+     <term><replaceable>type_name</replaceable></term>
+
+     <listitem>
+      <para>
+       The name of the data type of the transform.
+      </para>
+     </listitem>
+    </varlistentry>
+
+    <varlistentry>
+     <term><replaceable>lang_name</replaceable></term>
+
+     <listitem>
+      <para>
+       The name of the language of the transform.
+      </para>
+     </listitem>
+    </varlistentry>
+
+    <varlistentry>
+     <term><replaceable>from_sql_function_name</replaceable>(<replaceable>argument_type</replaceable> [, ...])</term>
+
+     <listitem>
+      <para>
+       The name of the function for converting the type from the SQL
+       environment to the language.  It must take one argument of
+       type <type>internal</type> and return type <type>internal</type>.  The
+       actual argument will be of the type for the transform, and the function
+       should be coded as if it were.  (But it is not allowed to declare an
+       SQL-level function function returning <type>internal</type> without at
+       least one argument of type <type>internal</type>.)  The actual return
+       value will be something specific to the language implementation.
+      </para>
+     </listitem>
+    </varlistentry>
+
+    <varlistentry>
+     <term><replaceable>to_sql_function_name</replaceable>(<replaceable>argument_type</replaceable> [, ...])</term>
+
+     <listitem>
+      <para>
+       The name of the function for converting the type from the language to
+       the SQL environment.  It must take one argument of type
+       <type>internal</type> and return the type that is the type for the
+       transform.  The actual argument value will be something specific to the
+       language implementation.
+      </para>
+     </listitem>
+    </varlistentry>
+   </variablelist>
+ </refsect1>
+
+ <refsect1 id="sql-createtransform-notes">
+  <title>Notes</title>
+
+  <para>
+   Use <xref linkend="sql-droptransform"> to remove transforms.
+  </para>
+ </refsect1>
+
+ <refsect1 id="sql-createtransform-examples">
+  <title>Examples</title>
+
+  <para>
+   To create a transform for type <type>hstore</type> and language
+   <literal>plpythonu</literal>, first set up the type and the language:
+<programlisting>
+CREATE TYPE hstore ...;
+
+CREATE LANGUAGE plpythonu ...;
+</programlisting>
+   Then create the necessary functions:
+<programlisting>
+CREATE FUNCTION hstore_to_plpython(val internal) RETURNS internal
+LANGUAGE C STRICT IMMUTABLE
+AS ...;
+
+CREATE FUNCTION plpython_to_hstore(val internal) RETURNS hstore
+LANGUAGE C STRICT IMMUTABLE
+AS ...;
+</programlisting>
+   And finally create the transform to connect them all together:
+<programlisting>
+CREATE TRANSFORM FOR hstore LANGUAGE plpythonu (
+    FROM SQL WITH FUNCTION hstore_to_plpython(internal),
+    TO SQL WITH FUNCTION plpython_to_hstore(internal)
+);
+</programlisting>
+   In practice, these commands would be wrapped up in extensions.
+  </para>
+
+  <para>
+   The <filename>contrib</filename> section contains a number of extensions
+   that provide transforms, which can serve as real-world examples.
+  </para>
+ </refsect1>
+
+ <refsect1 id="sql-createtransform-compat">
+  <title>Compatibility</title>
+
+  <para>
+   This form of <command>CREATE TRANSFORM</command> is a
+   <productname>PostgreSQL</productname> extension.  There is a <command>CREATE
+   TRANSFORM</command> command in the <acronym>SQL</acronym> standard, but it
+   is for adapting data types to client languages.  That usage is not supported
+   by <productname>PostgreSQL</productname>.
+  </para>
+ </refsect1>
+
+ <refsect1 id="sql-createtransform-seealso">
+  <title>See Also</title>
+
+  <para>
+   <xref linkend="sql-createfunction">,
+   <xref linkend="sql-createlanguage">,
+   <xref linkend="sql-createtype">,
+   <xref linkend="sql-droptransform">
+  </para>
+ </refsect1>
+
+</refentry>
diff --git a/doc/src/sgml/ref/drop_transform.sgml b/doc/src/sgml/ref/drop_transform.sgml
new file mode 100644
index 00000000000..59ff87cfe48
--- /dev/null
+++ b/doc/src/sgml/ref/drop_transform.sgml
@@ -0,0 +1,123 @@
+<!-- doc/src/sgml/ref/drop_transform.sgml -->
+
+<refentry id="SQL-DROPTRANSFORM">
+ <indexterm zone="sql-droptransform">
+  <primary>DROP TRANSFORM</primary>
+ </indexterm>
+
+ <refmeta>
+  <refentrytitle>DROP TRANSFORM</refentrytitle>
+  <manvolnum>7</manvolnum>
+  <refmiscinfo>SQL - Language Statements</refmiscinfo>
+ </refmeta>
+
+ <refnamediv>
+  <refname>DROP TRANSFORM</refname>
+  <refpurpose>remove a transform</refpurpose>
+ </refnamediv>
+
+ <refsynopsisdiv>
+<synopsis>
+DROP TRANSFORM [ IF EXISTS ] FOR <replaceable>type_name</replaceable> LANGUAGE <replaceable>lang_name</replaceable>
+</synopsis>
+ </refsynopsisdiv>
+
+ <refsect1 id="sql-droptransform-description">
+  <title>Description</title>
+
+  <para>
+   <command>DROP TRANSFORM</command> removes a previously defined transform.
+  </para>
+
+  <para>
+   To be able to drop a transform, you must own the type and the language.
+   These are the same privileges that are required to create a transform.
+  </para>
+ </refsect1>
+
+ <refsect1>
+  <title>Parameters</title>
+
+   <variablelist>
+
+   <varlistentry>
+    <term><literal>IF EXISTS</literal></term>
+    <listitem>
+     <para>
+      Do not throw an error if the transform does not exist. A notice is issued
+      in this case.
+     </para>
+    </listitem>
+   </varlistentry>
+
+    <varlistentry>
+     <term><replaceable>type_name</replaceable></term>
+
+     <listitem>
+      <para>
+       The name of the data type of the transform.
+      </para>
+     </listitem>
+    </varlistentry>
+
+    <varlistentry>
+     <term><replaceable>lang_name</replaceable></term>
+
+     <listitem>
+      <para>
+       The name of the language of the transform.
+      </para>
+     </listitem>
+    </varlistentry>
+
+    <varlistentry>
+     <term><literal>CASCADE</literal></term>
+     <listitem>
+      <para>
+       Automatically drop objects that depend on the transform.
+      </para>
+     </listitem>
+    </varlistentry>
+
+    <varlistentry>
+     <term><literal>RESTRICT</literal></term>
+     <listitem>
+      <para>
+       Refuse to drop the transform if any objects depend on it.  This is the
+       default.
+      </para>
+     </listitem>
+    </varlistentry>
+   </variablelist>
+ </refsect1>
+
+ <refsect1 id="sql-droptransform-examples">
+  <title>Examples</title>
+
+  <para>
+   To drop the transform for type <type>hstore</type> and language
+   <literal>plpythonu</literal>:
+<programlisting>
+DROP TRANSFORM FOR hstore LANGUAGE plpythonu;
+</programlisting></para>
+ </refsect1>
+
+ <refsect1 id="sql-droptransform-compat">
+  <title>Compatibility</title>
+
+  <para>
+   This form of <command>DROP TRANSFORM</command> is a
+   <productname>PostgreSQL</productname> extension.  See <xref
+   linkend="sql-createtransform"> for details.
+  </para>
+ </refsect1>
+
+ <refsect1>
+  <title>See Also</title>
+
+  <simplelist type="inline">
+   <member><xref linkend="sql-createtransform"></member>
+  </simplelist>
+ </refsect1>
+
+</refentry>
diff --git a/doc/src/sgml/reference.sgml b/doc/src/sgml/reference.sgml
index c52eb28c8c4..03020dfec42 100644
--- a/doc/src/sgml/reference.sgml
+++ b/doc/src/sgml/reference.sgml
@@ -111,6 +111,7 @@
    &createTSDictionary;
    &createTSParser;
    &createTSTemplate;
+   &createTransform;
    &createTrigger;
    &createType;
    &createUser;
@@ -152,6 +153,7 @@
    &dropTSDictionary;
    &dropTSParser;
    &dropTSTemplate;
+   &dropTransform;
    &dropTrigger;
    &dropType;
    &dropUser;